Design of Experiments Study on Scottish Wood Biochars and Process Parameter Influence on Final Biochar Characteristics

Abstract

Native Scottish wood samples were investigated as potential, locally sourced, raw materials for biochar production. Screening experiments identified pure softwood as the preferable feedstock. Influence of operational parameters, i.e. activating gas flow rate (CO2), heating ramp rate and contact time on final biochar characteristics, was investigated using design of experiments. Surface area and biochar yield were selected as response variables. Minitab was used to define experimental run conditions and suggested an optimal output at 60 min contact time and 15 °C/min ramp rate for maximum responses. The highest surface area (764 m2/g) was achieved at 850 °C from softwood, albeit with a low yield of 15%. Under optimised conditions, the observed surface area was 613 m2/g with ~ 18% yield. Pareto charts suggested no influence of gas flow rate on chosen responses, which correlated well with experimental data. Pore structure was a combination of micro- and mesopores with average pore widths of 3–5 nm and an average point of zero charge of 7.40 ± 0.02. Proximate analysis showed an increase in fixed carbon content from 20%, in the feedstock, to 80%, in the optimised biochar. Morphological analysis showed a layered carbon structure in the biochars. The results show the significance of the selected feedstock as a potential source of biochar material and the relevance of interplay of operational variables in biochar development and their final characteristics.

Aromaticity, polarity, and longevity of biochar derived from disposable bamboo chopsticks waste for environmental application

“…The aromatization process begins at approximately 350 °C and continues at higher temperatures [ 40 , 49 ]. The aromatic C–H deformation increased until the temperature reached 500 °C [ 43 ]. Amorphous carbons, the main biochar component, are structured as aromatic rings, giving biochar its characteristic stability [ 26 , 32 ].…”

“…The atomic ratio of H/C decreases substantially as the pyrolysis temperatures rise, indicating that depolymerization procedures are occurring, which implies increased oxidation resistance [ 3 , 10 ]. In biochar with an atomic H/C ratio lower than 0.7, this indicates the experience of the aromatization processes mainly at pyrolysis temperatures greater than 400 °C [ 13 , 16 , 27 ]; it has better fused aromatic ring structures [ 43 , 58 ], making it highly stable and resistant in the soil ecosystem [ 1 , 19 , 39 ]. Accordingly, the results found that pyrolysis of DBC feedstock at a temperature ≥450 °C provided DBC biochar which had a high degree of aromaticity with an atomic ratio of H/C lower than 0.7.…”

“…Previous studies reported that biochar could be produced from various lignocellulosic biomass feedstock types, both wooden and non-wooden [ 4 , 32 , 37 ], such as agricultural waste and residues [ 15 , 38 , 39 ], sewage and sludge [ 1 ], animal manure [ 34 ], and wood and woodchips [ 2 , 36 , 40 ]. Studies on converting wood-based wastes that have the potential to produce biochar have also been widely reported [ 5 , [41] , [42] , [43] ]. Disposable wooden chopsticks (DWCs) have been widely used worldwide, and most DWC wastes are destined for landfills and incinerators, which presents problems related to waste disposal and results in unsustainable natural resource consumption.…”

“…Additionally, in the case of the same feedstock type, the properties of biochar are significantly affected by the temperature [ 20 , 48 , 49 ]. However, wooden feedstocks have complex structures and compositions; as a result, the various components of the biomass break down at different temperatures, which makes the biochar properties highly diverse, even when produced from the same feedstock [ 41 , 43 , 50 ].…”

Influence of Pyrolysis Temperature and Time on Biochar Properties and Its Potential for Climate Change Mitigation

“…It has been widely observed that biochar can be produced from many types of lignocellulosic biomasses, such as rice husk [27], wheat straw [28], shell and peel [29], herbaceous [30], tree branches and bark [31], paper sludge [32], and manure [33,34]. Recently, researchers have given considerable attention to wood-based feedstocks due to their abundant availability and favorable characteristics [25,35,36], especially wood wastes, which generate and drive a circular economy. Single-use or disposable bamboo chopsticks (DBCs) constitute a large proportion of urban waste worldwide because they are used for food consumption in Asian cultures.…”